The present invention relates to devices for distributing data, and more particularly to star hub connection devices used in information display systems for coupling computers to peripheral devices.
Mid-range computers, such as an IBM 3X, AS/400.RTM. computer, generally communicate with several peripheral devices, such as terminals, printers, and the like, via a computer network such as an information display system, or more specifically a 5250 Information Display System. In such systems, the computer is typically referred to as the host, or the host computer.
Hosts often have one or more controller cards for controlling input/output functions. Each such controller card generally has several input/output ports, and each of these ports is typically capable of communicating with several peripheral devices. In one common information display system, each port of the host controller card is coupled to all of its associated peripheral devices via a connection device (or connector). The connection device typically has a host port, which is coupled to an input/output port of the host controller card, and several device ports, each of which is coupled to a single peripheral device. The connection device permits the input/output port of the host controller card to address each peripheral device that is coupled to a device port of the connector.
FIG. 1 shows one such prior art 5250 Information Display System 100 in which a controller card 110 of an AS/400.RTM. host computer, is coupled to two sets of seven peripheral devices 122 and 124 via a Gemini-2000 connection device 130 which is manufactured by Network Devices, Inc., of Sandwich, Mass. The Gemini-2000 connector 130 has two host transceiver ports 132 and 142 for communicating with the host computer controller card, and two sets of seven device transceiver ports 133-139 and 143-149 for communicating with peripheral devices. Connector 130 is a dual channel device with ports 132-139 forming the first channel and with ports 142-149 forming the second channel. Typically, each controller card of the AS/400.RTM. computer has eight input/output ports, and each of these ports is capable of addressing up to seven peripheral devices (however, each card can only address a maximum of forty peripheral devices).
In information display system 100, an input/output port 112 of the AS/400.RTM. controller card 110 is coupled to host port 132 of connection device 130, and an input/output port 114 of controller card 110 is coupled to host port 142 of connection device 130. The remaining six input/output ports 116 of controller card 110 are unused. Each device port in the first channel 133-139 is connected to one of the seven peripheral devices 122, and each device port in the second channel 143-149 is connected to one of the seven peripheral devices 124. Connection device 130 allows port 112 of controller card 110 to communicate with the first set of seven peripheral devices 122, and further allows port 114 of controller card 110 to communicate with the second set of seven peripheral devices 124.
FIG. 2 is a block diagram of the information display system 100 showing the internal topology of connector 130. Host port 132 is coupled to the device ports of the first channel 133-139 via a 1:7 star network 150. Similarly, host port 142 is coupled to the device ports of the second channel 143-149 via a 1:7 star network 152. A star network allows its host port to broadcast a signal to each of its associated device ports, and further provides each of the device ports equal access to the host port. Typically, signals applied to the host port from an input/output port of a controller card contain an address component and a data component. Such a signal is broadcast to all of the peripheral devices that are coupled to the star network, however, only the peripheral device having the proper address will process the data component of the signal.
Connection device 130 is typically referred to as dual star hub connector. The ports of the first channel 132-139 form a star hub connector 160, and the ports of the second channel form a star hub connector 162.
In the past, each peripheral device performed a single task and therefore could be fully accessed by the host computer via a single address. Such single address peripheral devices are now referred to generically as single-session peripheral devices. Each of the peripheral devices shown in FIGS. 1 and 2 are single-session peripheral devices. Today, multiple session peripheral devices, which can perform a plurality of tasks simultaneously, such as personal computers and other sophisticated devices frequently serve as peripheral devices for host computers. To fully utilize such a multiple session peripheral device, the host computer must communicate with the peripheral device via more than one address. Such multiple session devices are not to be confused with software generated multiple sessions that allow a single peripheral device to perform multiple tasks at the same address. In general, a peripheral device which requires two distinct addresses is referred to as a two-session device. Similarly, a peripheral device which requires three distinct addresses is referred to as a three-session device.
FIG. 3 shows an information display system 300 which illustrates a limitation associated with prior art connector 130. In system 300, input/output port 112 is connected to host port 132, two two-session peripheral devices 322 are connected to device ports 137, 138, and one three-session peripheral device 324 is connected to device port 139 of hub 160. Further, input/output port 114 is connected to host port 142, three two-session devices 326 are connected to device ports 143-145, and one single-session device 328 is connected to device port 146 of hub 162. Each hub 160, 162 is connected to a collection of peripheral devices that uses a total of seven distinct addresses. Since each input/output port of the controller card 110 can only supply a maximum of seven addresses, device ports 133-136 of hub 160 and device ports 147-149 of hub 162 must necessarily remain unconnected to any peripheral devices and are therefore wasted.
Prior art connectors such as connector 130 can only be fully utilized if all of the device ports are connected to single-session peripheral devices. If any one device port is connected to a multiple session device, one or more of the remaining device ports can not be utilized. Such ports add to the cost of the connector and yet they can not be connected to a peripheral device.
There is therefore a need for a connection device that provides the ability to connect a host computer to a variety of configurations of single and multiple session peripheral devices while providing for a higher utilization of the available device ports.
It is therefore an object of the invention to provide an improved programmable star hub connection device that can connect a host computer to a variety of configurations of single and multiple session peripheral devices while providing for a higher utilization of the available device ports.
Other objects and advantages of the present invention will become apparent upon consideration of the appended drawings and description thereof.